These assembly instructions make one Columbian Puzzle block. Repeat with each set of pieces chosen above to make 15 blocks total.
1. Mark a diagonal line on wrong side of light print and A print 3-1/2" squares. (To prevent fabric from stretching as you draw lines, place 220-grit sandpaper under squares.)
2. Align a marked light print 3-1/2" square with one corner of an A print 4-1/2" square (Diagram 1; note placement of marked line). Stitch on marked line; trim excess fabric, leaving 1/4" seam allowance. Press attached triangle open, pressing seam toward darker print, to make a pieced square A. The pieced square still should be 4-1/2" square including seam allowances. Repeat to make four total of pieced square A.
For a head start on coordinating decor, sew the cut-off triangles from the pieced squares into triangle-squares -- save and use for the pillows.
3. Repeat Step 2 using B print 4-1/2" squares and remaining light print 3-1/2" squares to make four total of pieced square B.
4. Referring to Diagram 2, sew together the B pieced squares in pairs; press seams in opposite directions. Join pairs to make block center; press seam in one direction.
5. Align two marked A print 3-1/2" squares with corners of a light print 8-1/2×4-1/2" rectangle (Diagram 3; note placement of marked lines). Stitch on marked lines; trim and press as before to make a side unit.
The unit still should be 8-1/2×4-1/2" including seam allowances. Repeat to make four side units total.
6. Referring to Diagram 4, lay out A pieced squares, side units, and block center in rows. Sew together pieces in each row. Press seams toward pieced squares and block center. Join rows to make a Columbian Puzzle block. Press seams toward center. The block should be 16-1/2" square including seam allowances.